Presently it is common to use a contact pad of lead to which a lead wire is connected by means of thermo-compression bonding. Disadvantages with the use of lead relate to the fact that thin lead films and fine lead wires are both mechanically fragile and sensitive to oxidation. These factors, plus the fact that niobium superconduts at 9.degree. K. while lead superconducts at 7.degree. K., become coupled with the fact that niobium is less fragile then lead and is less sensitive to oxidation, with the result that there has been greater use of niobium in making superconductor connections. If either the pad or the wire is made of niobium, it is undesirable to introduce lead into the process. Also, since the superconducting transition temperature is lower for lead than it is for niobium, it is advantageous to use niobium for both elements.
While these reasons exist for using niobium in superconducting connections, it has not been possible to make a reliable niobium bond. Superconducting contacts of niobium have been made to niobium films using pressure contacts for niobium wires or raised bumps on larger niobium terminals. An example of pressure contacts together with raised bumps is shown in U.S. Pat. No. 4,403,189. While reliable connections can be provided by these means, bulky and mechanically complicated structures are required to maintain the correct pressure for the contact in the face of extreme thermal cycling, which, in these cases, is room temperature to the temperature of liquid helium. Other types of clamps have been used to make electrical contact between a niobium wire or ribbon and a niobium pad. However, not only are they difficult to handle, a bond is not thereby made but it is merely a mechanically clamped connection.